142 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



surface have become more numerous. The examination of a series 

 of specimens such as those of which I give photographs here (pi. 

 30, figs. 1, 3, 5), which represent two individuals from station 5280 

 and a larger one from station 5661, clearly show that we have to do 

 with only a single species. 



The other characters which I invoked to separate O. mitis from 

 0. pulchra, taken from the radial shields, the mouth papillae, the 

 arm spines, and the double tentacle scale on the pores of the first 

 pair, are very well explained by the differences in the size and age 

 of the subjects. As for the number of the tentacle scales, it is not 

 always constant. Thus in the largest specimen from station 5280 

 (fig. 6) I find on the pores of the first pair sometimes a single scale 

 and sometimes two smaller scales. In the large specimen from sta- 

 tion 5661 (pi. 30, fig. 2) there is only a single tentacle scale on the 

 pores of the first pair, but this scale is very large ; on the other hand, 

 the number two is constant in the Siboga specimens with a disk 

 diameter of 18 mm. (fig. 7). This character therefore can not be 

 utilized for specific differentiation. 



It may be noticed that on the individual from station 5661, shown 

 in figure 2, the arrangement of the mouth papillae is a little irregu- 

 lar; there are sometimes four and sometimes five on either side; in 

 this connection I must recall a characteristic of O. pulchra which 

 struck me in 1904. As may be seen on the photographs of the speci- 

 men from station 5661 (fig. 2) and of the two specimens from sta- 

 tion 5280 (figs. 4, 6), there is found, between the outer mouth 

 papilla, which is more broadened than those preceding, and the first 

 under arm plate a small group of rounded and crowded granules, 

 from four to six in each group, which are somewhat unequal and of 

 which the outlines are not very well brought out. These granules 

 are usually very much more apparent in the large specimens, and they 

 are more difficult to detect in the small, where they remain very 

 slightly developed ; it is even necessary to be aware of their presence 

 to recognize them, and it is only in the small individual from station 

 5280, a photograph of which is given here (fig. 4), that they appear 

 at all clearly. 



These granules are analogous to those which I have noted in O. 

 globata and in 0. hastata and which H. L. Clark has found in O. 

 bytkiaspis. 



OPHIOPLINTHACA RUDIS (Koehler). 



Plate 24, figs. 1-6 ; plate 96, fig. 1. 



See for bibliography : 



Ophioplinthaca rudis KCEHLEB ('04), p. 132. H. L. CLARK ('15), p. 211. 

 Localities. Albatross station 5124; east coast of Mindoro; Point 

 Origon (N.) bearing S. 56 E., 38.45 kilometers (20.75 miles) distant 



